1. Field of the Invention
The present invention relates to a laser processing apparatus using a laser as a processing light source and, more particularly, to a laser processing optical apparatus suitable for repairing a circuit micropattern formed on a wafer during the fabrication of semiconductor circuit elements such as ICs and LSIs.
2. Related Background Art
Along with the rapid development of high integration semiconductor circuit elements in recent years, patterns formed on wafers have been miniaturized with higher precision. Under these circumstances, during the fabrication of semiconductor circuit elements, microdefects are often formed in their patterns. Finished semiconductor circuit elements as a whole become defective because of these microdefects and decrease the manufacturing yield. In order to increase the yield of a plurality of chips formed on a wafer during the fabrication process of semiconductor circuit elements such as ICs and LSIs, a technique is proposed to repair microdefects in a chip with a laser beam. A strong demand has arisen for an apparatus which can repair microdefects with a laser beam. When a wiring pattern in each chip on the wafer is to be repaired, the defective portion of the chip must be accurately irradiated with the laser beam, regardless of the different chip position on the wafer. However, conventional laser processing apparatuses have poor aligning precision when a chip is aligned with a predetermined radiation position. In VLSIs, for example, the line width of the circuit elements has become very small along with the development of micropatterning. A laser beam of a small spot size is required, and at the same time, the very small laser beam spot must be accurately aligned with the portion to be repaired. For this purpose, high precision position detection is essential. In addition, in order to increase the throughput of the wafer processing rate, laser power must be maximized. Thus, demand has arisen for an apparatus which satisfies the above requirements.